In general the kernel does not write to terminals directly, except for the console (Ctrl+Alt+F1), and even that only during system boot. You include a log level, which is a number enclosed in <> at the start of the string, and let syslogd decide where to send it (see syslog.conf(5); this will depend on what syslog package is used on your distribution). Don't try to change this or force the issue; aside from being obnoxious, there are some interesting locking and timing issues involved (consider what happens if you press Ctrl+s in the middle of it writing the log message).
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geekosaurApr 1 '11 at 1:19

I've noticed that either the kernel or some daemon, will write to my console when I insert or remove a USB drive.
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Tom ZychApr 1 '11 at 1:56

@Tom: That will generally be udevd; the kernel logs some information to syslogd as described above, but I don't think syslogd generally logs that to the console.
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geekosaurApr 1 '11 at 2:02